1. Field of the Invention
This invention pertains to controlled fracturing of earth formations. More particularly, this invention pertains to controlled fracturing by explosives and along either horizontal or vertical planes, or both, in a subterranean formation.
2. Description of the Prior Art
It was early determined that advantages could be obtained by fracturing of the earth's formations for a variety of purposes. In seeking to extract hydrocarbons from subterranean formations, the advantages attendant to fracturing became dramatically clear. Early attempts to fracture with explosives resulted in uncontrolled fracturing and destruction of tubing and other goods in the wellbore. Consequently, fracturing by explosives has been all but abandoned except in large diameter boreholes such as for exploding atomic bombs and the like. The controlled fracturing research efforts and development efforts have been directed into the field of hydraulic fracturing in which hydraulic pressure is imposed to create the fractures. Hydraulic fracturing is much less damaging, but is time-consuming and expensive. Moreover, such fractures have not proven to be as controllable as desired, nor able to be maintained within a desired strata or portion of the formation. On the contrary, the fractures have tended to orient themselves into the less desirable zones. For example, fractures have tended to become vertical and enter water producing zones or gas producing zones undesirably.
With the emphasis on the development of hydraulic fracturing, the explosives in a wellbore have been relegated to the areas of cutting off tubular goods, or jet perforating through tubular goods, and the like.
Thus, it can be seen that the prior art has not provided a method of controlled fracturing in a predominantly oriented plane or planes of the earth's formations for a variety of purposes.